The Laboratory of Neurobiology, part of the Medical Sciences Campus of the University of Puerto Rico, is an interdisciplinary and interdepartmental research facility which serves two functions: First, its collecting and holding facilities offer direct access to the rich Caribbean marine fauna, as well as to the many scientifically interesting invertebrate and plant species found in the rain forests of Puerto Rico. Second, it provides to both UPR and visiting scientists the necessary facilities to conduct research projects on the morphology (including ultrastructure), electrical activity, pharmacology and toxicology of the nervous system and other excitable tissues. The development of new preparations using locally available organisms and the study of biologically active compounds derived from the tropical fauna and flora is encouraged. Current objects include studies on the induction of electrical excitability in crustacean muscle by chemical modification of SH groups of membrane proetins; mechanism of antigen-induced conductance changes of the membrane of immunologically sensitized muscle cells; desensitization of cholinergic receptors using a technique of voltage clamp by drug iontophoresis; mechanism of the blocking effect of formamide on the excitation-contraction coupling mechanism of skeletal muscle; role of cyclic AMP on intercellular communication in the heart; development of heteromorph appendages in crustaceans and the role of proctolin, a peptapentide believed to function as a modulatory transmitter in insects and crustaceans.